Synthesis of carbon nanotubes and nano-necklaces by thermal plasma process

High-yield syntheses of peculiar carbon nanotubes and carbon 'necklace'-like morphologies have been obtained using a sophisticated thermal plasma technology. This method is based on a thermal plasma, which vapourizes the carbonaceous precursor in the presence of metal catalyst. Electron microscopy analyses provide evidences for a 'stacked-cup' structure for the carbon nanotubes. Carbon nano-'necklaces' are constituted by the repetition of multi-wall carbon spheres, connected along one direction in a 'bell'-like structure, and containing frequently an encapsulated metal particle. Microscopic growth mechanisms are also proposed to interpret both syntheses. Due to their intriguing topology, these new carbon nanotubes and necklaces may find important applications in nano-technology. (C) 2004 Elsevier Ltd. All rights reserved.